Imagine a huge international conference and every other seat around the enormous oval table occupied by a Donald Trump, each of them incessantly demanding the floor. How would you ever be heard?
Unfortunately that may be where we're headed, at least according to BBC Defence and Diplomatic Editor, Mark Urban.
The Irish prime minister, addressing a conference of Europe's centre-right parties, warned against "the dangers of populism", referring to the rise of left-wing parties in Spain and Portugal. Meanwhile, similar phrases about the populist spectre have been used in relation to the march of the right in Poland and France.
"Populism" in this context is simply democracy revealing growing electoral extremism or polarisation, and it extends far wider than Europe.
Pat Buchanan, an "outsider" candidate in three US presidential elections, notes: "Nationalism and tribalism and faith - these are the driving forces now, and they are tearing apart transnational institutions all over the world."
In Europe, mass migration has brought matters to a head. Unilateral actions, such as the decision this summer by Hungarian Prime Minister Viktor Orban to erect a border fence, have raised the pressure on other European countries and challenged the European Union.
...Reflecting on these dilemmas, Slovenian philosopher Slavoj Zizek wrote: "We definitely live in interesting times." He suggests the world may be approaching "a new era of apartheid", in which wealthier countries try to seal themselves off from war-torn, poverty-stricken ones.
Are a Trump or a Marine Le Pen really electable? Regardless of the answer, if the centre is shrinking, sapped by political insurgencies on the left and right, it becomes harder to rally support for unpopular international policies - whether they relate to trade, immigration or military action.
One has to look no further for the effect of this on any collective action than to see how some European countries have refused to accept supposedly mandatory refugee quotas, while others that ostensibly signed up to them dragged their heels.
Try to force the issue, as the European Commission's plans for a new border force could do, by inserting frontier enforcement units on to Europe's periphery - even against the will of the country concerned - and you risk a different kind of crisis.
With their national leaders beset by doubt and political polarisation, quite a few of Europe's political insurgents, from left and right, express their admiration for Russian President Vladimir Putin. (Ditto, for Donnie Trump)
Russia's recent troubles with Turkey show though that nations guided by ambitious strongmen are also making world politics less predictable as well as less harmonious. The Kremlin has unleashed economic sanctions on Turkey, after the shooting down of a Russian military aircraft, just as its actions in Syria led some to hope that Mr Putin might be about to patch up his relations with the EU.
As for the Middle East, a more assertive Saudi monarchy has waded into Yemen, Syria's President Bashar Assad is saying he won't stand down despite the gathering international peace effort, Israel's leaders are in no mood to restart a peace process with the Palestinians, and Iranian hardliners are promising to stand fast in defence of the oppressed Shia across the region.
In 2016 then, there will be big challenges to the international system - from the possibility of the UK leaving the EU, to the strains within the organisation caused by the ongoing migration crisis, sectarian violence in the Middle East, and increasingly ill-tempered trade disputes.
As nationalistic or left-wing rejection of the international system grows, pity the diplomats struggling for consensus.
Another aspect of this breakdown in international cooperation is that it may undermine any already slim hope of a collaborative effort to slash carbon emissions as needed to prevent runaway global warming. Those whom the gods would destroy....